Electric induction-furnace.



W. RODENHAUSER. 1 ELECTRIC INDUCTION FURNACE.

APPIJIOATION FILED NOV- 3, 19 08.

Patentsd 21, 1911 W. RODENHMTSER. ELECTRIC INDUCTION FURNACE.

APPLICATION FILED NOV. 3, 1908.

Patented Mar. 21, 1911.

2 SHEETS*SHEBT 2,

7 d WW/KWV UNITED STATES, r gnn'r WILHELM nonnnnausnn, or V6LKLINGEN-ON-SAAR, GERMANY, assis on 'ro THE GRGNDAL KJELLIN COMPANY, LIMITED, or LQNDUN, Enc ant ELECTRIC INDUGTION-FURNACE Patented Mar, 21, 191i,

Application filed November 3, 1908. Serial No. itiflfifiii.

To. all whom it may concern:

Be it known that I, Wlm-inmr Roman- HAUSER, a subject of the Emperor of Ger many, residing at 58 Poststrasse, Vtilkhngcn on-Saar, in the Empire of Germany, have invented certain new and useful Improvements Relating to Electric li'uluctionll'urnaces, of which the following a specification.

This invention relates to electric induction furnaces of the kind in which one or more ofthe limbs of the closed iron core, on which the primary winding is wound, are surrounded by continuous melting channels containing the material to be melted in such a manner that thecurrent for melting the material in the melting channel or channels is produced directly .by he induced currents set up in the material to melted, which serves a single secondary winding. Owing to the relatively great distance of the secondary winding (the material. to be melt ed) from the iron core, great magnetic-dispersion is produced; this dispersion entails, as is known, great phase displacement thus rendering necessary the use of currents of low periodicity and hence involving the we of costly current-generating plant; likewise making it impossible to connect the furnace to a. current-generating system which has to supply other appliances fed by high periodicity current.

It has already been proposed to reduce the dispersion by arranging a secondary wire or bar winding upon the core limb itself, the current induced in this winding being conducted to thelnate'rial to be melted by the aid of electrodes inserted int-he wall of the furnace. It has not, however, been found possible to obtain thoroughly satisfactory results in this way because a secondary winding so arranged does not remove the defect to an extent commensurate with the complication of the arrangement, and because on the other hand, if an arrangementfor utilizing the current of the secondary winding is not provided, so that this winding is short circuitetl on itself, much electrical energy is lost by the generation of ohmic heat in the winding. i i

The chief object of the present invention is to reduce the dispersion in a yery simple but effecti e manner by means of a special formation of the cross section of the limbs or members of the closed iron core, and a members compose novel arrangement of This arrangeinei'it 1s ing the said core. based upon a knowledge 0 the fact that tar greater number of lines of magnetic dispersion issue from the limbs at. the two faces that are formed by the of the compressed sheet metal lamime composing the limbs, than from the faces torred by the two outer sides oi the two c metal laminae. As is known, the reason for this is that ftheeddy currents circulating in the laminae act opposition to the dispersion of the'linesot force from the iron core in a direction tra'nsrcrse to the lami. According to the present invention the dispersion above referredv to making the faces constituted by the on most sheet metal laniinzc conside 1y broader than the faces formed by the edges of the compressed laminae; in other Words each lamina is ctmsidcii'ahly broader than the thickness of the assemblage of (56331- pressed laminae. By this means limbs which present an elongated rectangular form in cross-section are obtained the melting channels which inclose the rectangular limbs formed in th s manner is of course greater than if the cross section of the limbs were of square or circular shape in cross section other conditions being the same. terial in the melting channels to the passage of the current induced in it is therefore in- ()LQtt.3d, and this increase in resistance of the secondary circuit causes a reduction oi the phase displacement, and this, as

luiown, produces a favorable eii'cct in the working 01 the furnace.

caution against magnetic dispersion at the As afurther pr ed oi the laminae, the joints between the yoke pieces and vertical limbs comprising the iron core should be such as to cover as much as possible the faces constituted by the edges of the laminm, and cause the laminm of one member to be continuous with those of its adjacent members. This is the case if the plane in which the extremity of the central lamina oit yoke piece lies it'lentical with that, in which the adjacent extremity of the central lamina. of the cor responding vertical limb lies.

In applying the principle of this invention to electric induction furnaces in which the core comprises two straight horizontal yoke pieces lying at right angles to and con rinost sheet is rcdnceo. bj

The length of The resistance opposed by the me -working hearth, the ion er cross sectional axes of the two rectangu ar limbs would be in a line with one another, the yoke pieces extending in the same line between the said limbs. it will readily be understood, how- .ever, that this! would result in-a defective :form of furnace; the furnace would be disproportionatly long and narrow in plan, and the melting chamber formed by the union of the two melting channels surrounding the limbs and serving as the working hearth would be small. are avoided and the working conditions rendered favorable by arranging the vertical limbs in such a manner that their broad side faces are directed toward each other and their short-cross sectional axes are in line; by this arrangement the furnace may be such 7 that its form in plan does not differ largely from a square, and the melting chamber or working hearth may be given a very extended area. As however, with this arrangement of the vertical limbs, their central laminar are not in the same plane but in parallel planes, separated by the distance between the limbs, it follows that, if the requirement referred to above, namely that the lamina: of the vertical limbs and yokepieces shall be continuous at the joints, is to be fulfilled, the two yoke pieces connecting the ends of the vertical limbs cannot be formed straight bars but each yoke must'be curved in such a manner that its two ends, which are to abut against the ends of the vertical limbs, are similarly directed. Prefcrably the yoke pieces are bent semi-circularly, the inner diant ter of this semicircle being equal to the horizpntal distance between the oppositely placetkfaces of the two vertical limbs. The plane ofthe circle into which each yoke piece is bent must be perpendicular to the planes in which the laminac composing the vertical limbs lie; it maylie either 'in the piano containing nal axes of the two vertical limbs or be perpendicular thereto, that is to say it may be horizontallY directed. The last-named arrangement presents special advantages; in

the first place the co v'Ql plates of the melting chamber, or a working door arranged, say, in the cover of the furnace, are rendered readily accessible and can readily be removed for effecting repairs to the furnace or the like; secondly, the upper yoke piece be- 1ng, 1n accordance with this invention, very narrow compared with its depth, covers only a very small part of the furnace, and need not therefore be removed each time the furnace is prepared for smelting.

Polyphase current transformers have not hitherto been used for electrical induction furnaces, although the'advantages presented Both these defects the longitudiby the use of polyphase currents for factory installations as compared with ordinary alternating currents are well known, for the reason that in using transformers of known construction the furnace has not been accessible and has been difiicult to supervise. In accordance with the present invention. however, polyphase current transformers .may readily be used without any constructional complications; their use secures the limbs arranged triangular-1y have not been used for the reasons given, it was necessary to provide special and complicated means.

In order that the said invention may be clearly understood and readily carried into effect, I will describe the same more fully with reference to the accompanying drawings, in which Figure l is a vertical section, Fig. 2 a sectional plan, and Fig. 3 a vertical section at right angles to the position in which l ig. 1 is taken, illustrating one form of.furnacc constructedin accordance with this invention. Fig. 4 is a sectional plan of a furnace constructed in accordance with this invention for use with three-phase current.

In each of the figures 1.4 represents the common melting chamber or hearth formed by the union of the melting channels (Z which 105 Referring first to Figs. 1 to 3 it will be seen that the furnace is about one and one 110 half times as long as it is wide, and that the width of the laminae of which each of the limbsq is composed is about three and one half tims ascgreat as the thickness of the assemblage. of laminae. two yoke pieces. b, which are bent scmicircularly and connect the ends of the limbs c as shown, is arranged in such a manner that it lies in a horizontal plane with the result that free door 6 arranged in the middle of the furnace cover and serving for the introduction of fluxes or thelike into the melting hearth a. The lower of the two yoke-pieces is arranged in such tainingthe longitudinal axes of the vertical limbs; by this arrangement the lowefr yoke P1808 b and the two limbs c 0 may consist of one piece as shown.

In Fig. 4, which represents a furnace for 130 current transformer furnaces with vertical The upper of the access can be had to a working 12o a manner that it lies in a plane con- (c are arrange .use with poly'phase eurrpht two of the limbs in the same relative positions as the two limbs in the furnace illustrated in Figs. 1 to 3. .The third limb is arranged with ts longer cross-sectiopal axis at right angles -to those of the otl 'i two, and is so situated that the longitudinal axes of the three limbs are loelttpd in plan approximately at the corners of an equilateral triangle. The two ends of each of the two first named limbs-are connected with the ends of the third limb by horizontal yoke pieces I) which are curved approximately like a quad- 7 by the union of the'three melting channels (1 inclosing the said limbs is of up roximatelyrectangular shape in plan in t e arrangement shown in Fig. 4, as is also the case with the furnace shown inFi s. 1 to The cover: plate .or .platcs'(not shown) serving for coverin the working hearth a,are readily aceessib er an electrode f, consisting of aplateimfrefractory-material facing-the nia Q -tcrial*'iii';; the' melting chamberfand a metal plate"betweemrsaid refractory'material and working the furnaee' wall, maybe. let into each of .those parts fofthe furnace wall wh ch are "situated between'two limbs and servetoconfine the working hearth n; a stx-onda'ry wire or bar winding .may be arranged upon one or more ofthe vertical limbs ainf 'theccurrent induced in this winding may be conducted to the'electrodes f in such a manner that the alternatin currents conducted through the earth ain tlt'isfi manner flow through the material to be melted in the same direction as thecurrents produced in the melting channels by direct induction. This arrangement,which'docs not however form a novel part of the-present invention,

insures the material contained in the large working hearth being traversed, in addition to the direct induction currents, by alternating currents of such strength corresponding to its large cross sectional area and consequently to its small resistance that the heat,

produced in the workin hearth is not much less than the heat pro need in the melting charnels. The use of a polyphase current furnace with its vertical limbs arranged tri angularly'in plan, whatever may be the form of'the limbs in.cross section or the method of arranging the yoke-pieces connectin-g tlu-ir ends, insures that a circulatory movement of thc material is obtained in the working heartlra arranged in the space between the three limbs, 'and. as is known,

this circulation acts beneficially on the met-l allurgical process carried out in the furnace.

\Vhat I claim and desire. to secure by Let tcrs Patent of the United-States is 1. In an electric induction furnace, the combination with the primary winding and the melting chamber, of a core on which the n'iinary winding is wound, said core piercing the hearth and comprising sheet metal lamina: the width of each'of which'is considerably greater than the total thickness of the assembled laminae, the broad face oi said core facing the open working portion of the hearth, for the purposes specified. j

2. In an electric induction furnace, the combination with the primary winding and the melting chamber, of a core on which the primary winding is wound, said. core piercmg the hearth and-comprisingsheet metal laminae. assembled together into elongated rectangular form in cross section, the. planes containing the laminae lying parallel with portion of fied.

combination with the primary windiiig "and the melting chamber, of vertical limbs INQIC- ingthe hearth and connecting yoke pieces of sheet metal laminae the width (if eachof which is greater than the total thickness of the assembled laminae, the broad face of saidvertical limbs facing the open working portion of the hearth, the laminae of abutting portions of the limbs and-yoke pieces being continuous, for the purposes specified.

4. in an electric induction furnace," the comb nation with the primary winding and ing the hearth and connecting yoke pieces constituting a closed iron core, and composed of sheet metal laminae the width of each of which is greater than the total thickness of-the assembled laminze, the broad face of said verticallimbs facing the open working portion of the hearth, the said yoke pieces being bent so that their extremities are similarly directed, and the laminae and abutting portions of the IimbsfandQyoke pieces being in the same plane so as to be practically continuous, .for. the purposes specified.

5. In an electric induct-ion furnace, the combination with the" primary winding and the melting chamber, of two vertical limbs and yoke pieces cons'tituting'a closed iron coreand composed of sheet metal laminae, the width of eachof which is greaterv than the lamina, said vertical limbs piercing the hearth and having their broad sides facing the open working portion of the hearth, the shorter axes of the two vertical limbs being arranged in line with one another, and the yoke pieces bent so that their extremities are in the same plane,- so as to be practically 8.5 the longer axes and facing the open working the hearth, for the purposes speci-' 1 3. In an. electric induction furnace, th'e constituting a closed iron core and cmnposed the melting chamber, ofwcrtical limbs pierctotal thickness of the rectangularly assembled similarly directed, the laminae of abutting portions of the limbs and yoke pieces being in the same plane so as to be practically con tinuous, for the purposes specified.

(3. In an electric induction furnace, the:

(":lfll'lllltltlOll with the primary \rii'iding, and

the, melting chamber, of two vertical li'znhs and yoke pieces constituting a closeriron 5 core and composed of sheet metal lam na: the width of each of which 18 greater than tral lamina: of abutting portions of tbe'lim'bs' the total thickness of the rcctanqularly assembled laminae, said vertical lllllUS piercing the hearth and having their broad sidesfacing the openworking portion of the hearth, the shorter axes of the two vertical limbs being arranged in line with one another, and the yoke pieces bent so that their extremities are sinularly directed and the upper of the yoke pieces being arranged 20'. horizontally, the laminae of abutting porand horizontal yol-ze pieces bent so as'to jam the extremities of the vertical limbs, the said lunbsand yoke pieces comprising a closed llOXl' core, being constructed of sheet metal laminae the width of each of which is greater than the total thickness of the assembled laminar, andarranged with the broad sides of the vertical limbs facing the open working portion of the hearth.- and the lamina: of abutting portions of the limbsand yoke pieces being in the same plane so as to be practically continuous. for the purposes specified.

8. In an electric induction furnace, the combination with the primary winding, and the melting chamber, of two vertical limbs of elongated rectangular form having their shorter axes in line with one another, a'third vertical limb of similar form located triangularly with respect to the other two and baring its shorter axis at rightanglcs to-those of the other two, and horizontal yokepieces bent so as to join the extremities of the 'ver-' tical limbs, the said limbs and yoke pieces comprising a closed iron core and being constructcd of sheet metal laminae the widthf ofa.

each of which is greater than the total-thick? ness of the assembled laminae and the cn'--- and yoke pieces being in the same plane so as to be practically continuous, for the p'urposes specified. v

f). in an electric induction furnace,-'t-he' combination with the primary winding and the melting hearth, of vertical limbs piercing the hearth, and connecting yokev pieces constitutinga closed iron core and composed of sheet metal lamina, the width of each of which is "greater than the total thickness of the assembled laminae, the broad faces of 5 said vertical limbs facing the open workin portion of said melting hearth, as descri 10. In an electric induction furnace, the combination withth primary winding, and the melting chamber, of two vertical limbs of elongated rectangular form having their shorter axes in line with one another, a. third ,vertical limb of similar form located triangularly with respect to the other two and having its shorter axis at right angles to those'of the other two,-:a'nd horizontal yoke pieces bent so as to join the extremities of the vertical limbs, the said limbs-and Okepieccs comprising a closed iron core in being constructed of sheet 'metal laminae the width of each of which is;greater;than the total thickness of the assembledtlaminae d the central lamina: of abuttin'g*limb% yoke pieces being in the same planeggogis to be practically continuous for the specified. 4

in testimony whereof {I atlix my signature in presence of two witnesses. VVILHELM ODENHAUSER \Vitnesses: 1'

'LoUIs VANnonY,

H. STELzEn. 

